Controlling inductive heating



Jan. 14, 1947. F. s. DENNEEN ET AL 2,414,141

CONTROLLING INDUCTIVE HEATING Filed Nov. 12, 1942 Patented Jan. 14, 1947 UNITED STATES PATENT OFFICE CONTROLLING INDUCTIVE HEATING Francis S. Denneen, Cleveland, and William C. Dunn, Shaker Heights, Ohio, assignors to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Application November 12, 1942, Serial No. 465,518 Claims. (Cl. 219-13) This application is a continuation in part of our application Serial No. 337,424 for Apparatus for hardening tapered articles, filed May 27, 1940, now Patent No. 2,309,631, which application is a continuation in part of our earlier application Serial No. 54,388, filed December 14, 1935, now Patent No. 2,202,759, and relates primarily to apparatus and method for heatin cylindrical articles having a single tapered surface and is more particularly directed to inductively heating a zone of the tapered surface.

The art of' inductively heating and then quenching a surface zone of an ordinary cylindrical article is well known. Inductively heating and the quenching a zone of a double conical surface has been taught in the parent application Ser. 337,424, However, the heat treatment of a surface zone of a single conical element requires apparatus and method differing from those heretofore used in the heat treatment of other surface zones.

Since current induced in a surface zone of an approximately cylindrical article by current flowing in a conductor extending circumferentially around the zone flows circumferentially in this surface zone, any change in a distribution of the current in a cross section of the conductor will effect a change in distribution of current in a section of the surface zone. Also, when high frequency current is employed, any variation in spacing between the conductor and the surface zone will affect the distribution of current in the zone. Further, any difference of diameter of a part of the surface zone not only controls the amount of metal bein heated in that part, but

controls the circumferential length of the circuit through which the induced current flows.

The present invention has been for the purpose of meeting these conditions by providing a correct distribution of heatin current in a surface zone of a tapered part of a shaft or similar article which our investigation has revealed requires an inductor of a form difiering from that of inductors heretofore employed. Accordingly the general object of our invention has been to provide an inductor capable of controlling a distribution of heating current in a surface zone of a tapered article. Another object has been to provide means for adjustably supporting and locating the article correctly relative to the inductor employed. A still further object has been to provide a generally applicable method zone. Other objects will become apparent from the following description.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means and steps hereinafter fully described and particularly pointed out in the claims; the annexed drawing and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various ways in which the principle of the invention may be used.

In the said annexed drawing:

Fig. 1 is a plan view of one form of apparatus employed in the practice of our invention.

Fig. 2 is a section substantially on line 22 of Fig. 1.

Fig. 3 is a section as indicated at 3-3 in Fig. 2.

In the form ofthe apparatus illustrated the current conducting member comprises an upper part 10 and a lower part ll, separated throughout the greater part of their perimeters by the circumferential dividing slot !2 and joined at selected points by bridge elements I 3. xcepting for the circumferential dividing slot the conductors present a substantially continuous conical inner surface 14, which surface is adapted to lie adjacent to the conical surface I5 of the article It being hardened. The angle included between opposite elements of the inner conical surface of the conductor is less than that between opposite elements of the surface of the article, thus providing a closer magnetic coupling in the region of greater diameter of the cone of the article where both a greater periphery and a greater mass of metal require greater heating.

The two conductors l0 and H joined as shown are formed to provide an exterior channel 20 which channel in cooperation with annular cover 21 serves as a reservoir for cooling fluid which is supplied by the valve controlled conduit 22. The cover is separated from the conductors by gaskets 23 and is held in assembled relation with the conductors by means of disc or plate 24 which through insulating ring 25 is disposed to bear against an annular face of conductor 10. Screws 21 pass through holes in a peripheral part of the disc 24 and threadedly engage holes in a peripheral part of cover 2| to wedgingly compress gaskets 23 between peripheral parts of inner conical surfaces of the cover and exterior conical suriaces of the conductors and thus to hold the parts in assembled relationship.

. of procedure in the heating of a tapered surface Cover 2| is supported by base 30 which carries --adjustable centering member 3| for holding article IS in correctly centered position in the inr of airgaps at opposite ends occurs.

ductor and at the correct elevation. The concluctors It and II have cuts at 32 with terminals such as 33 and 34 connected to the conductors at parts adjacent to the cuts, the terminals serving as means for supplying current to the conductors from some suitable source such as leads 36 and 3'2; connected to a highfrequency generator.

The inductor comprising members I (l and H can readily be replaced by another when it is desired to heat treat a conical article of a different form or size. Support 3| can then be adjusted to bring the article into correct position relative to th inductor or this support can be replaced by another better adapted to engage a part of the article to be heat treated. The support employed is usually threaded into the base 39 and held in position by lock nut 39.

It will be observed that in axially'adjusting the position of the conical portion of article l6 ininductor it the rate of change of air gap at the larger-diameter is muchrgreater thanthe rate of change of air gap at the smaller diameter, i. e., by. axially adjusting the position of the-article'in theinductor a substantialchange in ratio. Thus, the airgap at the largediameter canreadily be reduced to a very small amount, while the air gap at the small end, although reduced, remains of considerable amount. Hence, by axially shifting, the article in the inductor and selecting a proper frequency of current being supplied by leads 3% and 31' such as by=changing speed of a high frequency generator-supplying the current and/or by changing the power being delivered by suitable field regulation of the generator, a very accurate control for a distribution of heating in the 'surface zone of the conical portion is attained, such as in the extent of the heated .part of the zone and in'itsdepth contour. To attain a proper distribution of heating, in some cases the elements of the inner surface of the inductor are not always straight lines but are curved to provide a greater or lesser airgap at the central part of the, inductor according the. heating desired and frequency and power available. Other forms may be employed embodying the 'features of our invention instead of the one'hereinexplainednhange being made as regards the vmeans. and the steps herein disclosed, provided the. elements-stated by any of the following claims or. the equivalent of such stated elements be employed, whether produced by our preferred method or by others embodying steps equivalent to those stated in the following claims.

We therefore. particularly point out and distinctly claim as our invention:

1; In apparatus for'heating a surface zone of 'a substantially conical portion of, an axially ex- .tending:article, an inductor comprising substantially .two parallel current'conducting sections of generally'conical form adapted to extend peripherally of the conical portion, one of. said sections being of varying thickness to control a distribution ofeurrent.flowingperipherally in the said-one section, and means for supplying periodically varying current to said inductor.

2. In a method of heat treating surface zones 4 diameter in a conductor closely spaced to the conical surface of the said end, flowing current around the end of lesser diameter in a conductor spaced from the conical surface of the end of lesser diameter, the conductor lying adjacent to he end of larger diameter being more closely spaced to the conical surface than the conductor lying adjacent to the end of smaller diameter,

moving the article axially to simultaneously vary the space between the end of larger diameter and its adjacentconductor and th end of smaller diameter and its adjacent conductor, maintaining the conductors in substantially parallel spaced relation with each other, and supplying inducing current to said conductors to flow in parallel therethrough to induce heating current in conical surface zones of both ends of the conical part of the article.

3. In a method of heat treating surface zones of a generally conical part of an article, a diameter at. one end of the part being greater than a diameter at an opposite'end, the steps comprising flowing current around the end of the greater diameter in a conductor closely spaced to the conical surface of the said end, flowing current around the end of lesser diameter in a conductor spaced from the conical surface of the end of lesser diameter, the conductor lying adjacent to the end of larger diameter being more closely spaced to the conical surface than the conductor lying adjacent to the end of smaller diameter, moving the article axially to simultaneously vary the space between the end of larger diameter and its adjacent conductor and the end of smaller diameter and its adjacent conductor, maintaining the conductors in substantially parallel-spaced relation with each other, supplying inducing current to said conductors to iiow in parallel therethrough, and flowing more current in parts of the conductors remote from each other than in adjacent parts of the conductors to increase heating in opposite ends of the conical parti. In apparatus for heating a'surface zone of a generally conical portion of an axially extending article, an inductor comprising two substantially parallel generally conical conductors adapted to encircle adjacent parts of the conical portion and to lie in closely spaced relation with said parts, one of the conductors being disposed to lie in'cioser relation to its encircled part than the other conductor lies to its encircled part, means for supporting the conical portion substantially co-axially with the conductors, means :for adjusting the supporting means to vary the space between the conical portion and each of the conductors, and meansfor flowing inducing current through the conductors to heat the adjacent parts of the conical portion.

5. Inapparatus for heating a surface: zone of a generally conical portion of anaxiallyextending article, an inductor having a, substantially conical inner surface adapted to lie adjacent to the surface zone, an annular groove in an "outer surface of the inductor, an annularly disposed cut in a root portion of the groove dividing the inductor into two substantially parallel. conductors,

a plurality of bridge elements spacedalongithe cut holding the conductors in-spaced' relation with each other; andmeans for supplyingiinducing current to theinductor.

' FRANCISS. DENNEEN.

- ,WILLIAM C;'.DUNN. 

